Switch actuating device



Oct. 20,. 1942. CRUM 2,299,309

SWITCH ACTUATING DEVICE Filed Oct. 13, 1939 Fig.1

Patented Oct. 20, 1942 SWITCH ACTUATING DEVICE Stephen Cram, Minneapolis, Minn., assignor to Minneapolis-Honeywell Regulator Minneapolis, Minn, a corporation of mpany, Delaware Application October 13,1939, Serial No. 299,317 6 Claims. (Cl. 200-155) This invention relates generally to actuating devices for switches and is more particularly directed to a mechanism for adjusting the dinerential of operation of a switch which is controlled in accordance with the variations in a variable condition.

It is old and well known in the ;prior art to obtain a differential adjustment on an automatic switch by means of a lost motion connection between a condition responsive device and the switch actuated thereby, said lost motion connection comprising a pin extending within a tapered slot. The pin in most cases is adjustably mounted directly on one of the parts which are moved by means of the condition responsive device for actuating the switch. In order to adjust the operating differential of the switch in a device of this type it is necessary to manually vary the position of the pin on the movable member upon which it is mounted. If this is done carelessly, or by some unskilled hand, it is quite possible that the moving parts may be damaged or too great a strain placed on the condition responsive device so that it is permanently deformed or the calibration upset. It is therefore seen that an adjustment of the differential is a dellcate one requiring skill and care in prior art devices of the pin and slot type.

It is a primary object of the present invention to provide an automatic switching device having a pin and slot type of differential adjustment wherein the member for adjusting the difl'erential is mounted on a fixed support so that no damage can be done the moving parts of the device by adjusting the operating diflerentia'l, even though this adjustment be made carelessly by one not skilled in the automatic switching art.

Another object of the invention is to rotate a member having a tapered slot in response to variations in a variable condition, drive thereby a switch actuating member having a pin inserted in said slot, and vary the operating differential of said switch actuating member by bodily moving said switch actuating member and pin with respect to said tapered slot.

Still another object is to shape one edge of the slot so that the condition value at which the switch is actuated in one direction will remain the same regardless of the differential adjustment.

These and other objects will become apparent as the following specification is read in the light of the accompanying drawing, in which Figure 1 is a front elevation of the switch actuating mechanism,

Figure 2 is a rear view of part of the mechanism shown in Figure 1, and

Figure 3 is a section taken along line 3-3 of Figure 2.

Referring now to Figure 1 of the drawing a base I l is used to support the switch actuating mechanism and also to support a condition responsive device which may extend rearwardly of the base. This condition responsive device may well take the form of a coiled bimetallic thermostat and may be mounted on the base H in the same manner as shown in my copending application Serial No. 299,316, filed October 13, 1939. The bimetallic element may be rotatably adjusted by means of the adjusting arm I! as shown in the aforementioned application and on variations in temperature may rotate the operating rod l3 shown in Figure 3.

A plate I4 is rigidly connected to the base II by means of the posts l5 and screws It. A differential adjusting lever H is pivotally mounted at one end to the plate I4 as shown at l8. The spring element I9 is mounted concentrically with the lever l1 and offers a certain amount of frictional resistance to the rotation of the lever I! so that this lever will always remain in its adjusted position. The lever I1 is provided with a forwardly extending finger 20 which cooperates with a scale 21 on the plate H to indicate the relative adjustment of this lever. The plate It is provided with a pair of shoulders 22 and 23 which limit the amount of movement which can be given the lever IT.

A shaft 25 is pivotally mounted through an intermediate portion of the lever H by means of a sleeve 24 rigidly carried by lever l1 and a switch carrying member 26 is rigidly connected to the shaft 25 at the front of the plate It. The member 26 carries a mercury switch clip 21 which in turn supports the mercury switch 28. The lower end of the clip 21 is bifurcated as shown at 29 and between the bifurcations an eccentric screw 30 is rotatably mounted in the switch carrying member 26. Rotation of this screw 30 will rotate the switch clip 21 about the shaft 25 to provide a calibrating adjustment whereby the switch may be properly aligned on the carrier 26. Rigidly mounted on the other end of the shaft 25 at the rear of the plate [4 is a crank arm 32 having a rearwardly extending projection 33. As the switch carrier 26 and crank arm 32 are both rigidly connected to the shaft 25 any rotation of the crank arm 32 will be transmitted to the carrier 26 to rotate the mercury switch 28.

The end of the operating rod I3 carries a hub 35 which may be held in any rotative position about the operating rod l3 by means of the set screw 36. The hub 35 rigidly carries an operating arm 31 which is provided with a tapered slot 33 through which the projection 33 on the crank arm 32 extends. It will therefore be seen that as the operating rod I3 is rotated in response to temperature variations by the bimetallic thermostat that it will rotate the crank arm 32 and hence operate the mercury switch 23.

Assuming that the temperature is at a relatively low value and the switch has been actuated to closed position as shown in Figures 1 and 2 of the drawing and the temperature to which the bimetallic element responds begins to increase the operating rod l3 will begin to rotate in a clockwise direction as seen in Figure 2. With the lever I! adjusted to an intermediate position as shown, the projection 33 on the crank arm 32 will be in an intermediate position with respect to the length of the tapered slot 38. The tendency of the mercury switch 23 is to remain in the position to which it has been actuated and therefore as the operating rod l3 starts to rotate in a clockwise direction in Figure 2 it will first move the operating arm 31 until the side 40 of the slot 38 engages 'the projection 33 on the crank arm 32. A further rotation of the operating rod l3 in the same direction will then cause a rotation of the crank arm 32 in a clockwise direction and the mercury switch 28 will be moved to open circult position. As the temperature at the bimetallic thermostat begins to decrease as a result of opening the switch 28 the operating rod i3 will begin to rotate in a counter-clockwise direction and the first movement of the operating arm 37 will first separate the side 43 from the slot 30 from enengagement with projection 33 and cause the side M of this slot to engage the projection 33 and actuate the mercury switch to closed circuit position again. It will be understood that while the lost motion provided by the slot 33 and projection 33 is being taken up the mercury switch remains substantially stationary.

In order to adjust the extent of this lost motion and hence the operating difierential of this switch the lever H is rotated about the shaft 83. If it is desired to increase the difierential, the lever i1 is rotated in a clockwise direction as seen in Figure 2. This movement will raise the shaft 25 which carries the mercury switch 23 and the crank arm 32 with its projection 33. The projection 33 will then be located in a wider part of the tapered slot 33 and hence the amount of lost motion will then be greater. If it is desired to decrease the differential the lever ii is rotated downwardly which will bring the projection 33 to the narrow part of the slot 33 and hence decrease the amount of the lost motion.

It is desired in this device that the temperature value at which the switch is moved to open position should not be varied by adjusting the operating diflerential of the switch. Therefore the side 40 of the slot 4| is so shaped that as the arm 31 is rotated in a clockwise direction as seen in Figure 2 the mercury switch 28 will be moved to open circuit position at the same temperature value regardless of the position of the projection 33 longitudinally of the slot 33. In order to accomplish this the side 40 is in the shape of an are having the center of the shaft I3 as its center when the mercury switch carrier is in its vertical position and the mercury switch in its break position. Therefore when the parts are in the position where the mercury switch 28 is just about to be opened a rotation of the lever M will not produce any rotation of the crank arm 32. The side M of the slot 38 is so shaped that the amount of lost motion progressively increases as the lever I! is rotated from engagement with the stop 23 into engagement with the stop 22.

It will be noted that the difierential adjusting mechanism of this device is pivotally mounted to a fixed plate l4 and therefore no strain can be placed on the bimetallic thermostat or on the operating member by a careless manipulation of the difierential adjusting lever 51.

This control device has been described as being operated by means of a coiled bimetallic thermostat. it will readily be appreciated however that any type of condition sensitive element capable of rotating the operating rod i3 may be substituted without the use of invention.

As certain changes and modifications in this device may occur to those who are skilled in the art I wish it to be understood that I intend to be limited only by the scope of the appended claims and not by the specific embodiment disclosed.

I claim as my invention: I

1. In combination, a switch operable between open and closed positions, a, first arm for operating said switch, a sensitive condition responsive element, a second arm connected to said element for rotation thereby upon variations in said condition, one of said arms having an oper ng of varying width therein and the other of said arms carrying a projection entering said opening to form a, lost motion connection, said element causing transverse motion of said projection in said opening to provide a differential between the values of said condition which cause actuation of said switch in opposite directions, a fixed support, means mounted on said fixed support for bodily shifting said first arm and said switch to cause motion of said projection lengthwise of said opening and thereby vary said differential, and a pivotal connection between said first arm and said shifting. means for permitting free transverse movement'of said projection in said opening, thereby preventing transmission of torque from said shifting means to said sensitive element.

2. In combination, a switch operable between open and closed positions, a first arm for operating said switch, a sensitive condition responsive element, a second arm connected to said element for rotation thereby upon variations in said condition, one of said arms having an opening of varying width therein and the other of said arms carrying a projection entering said opening to form a lost motion connection, said element causing transverse motion of said projection in said opening to provide a differential between the values of said condition which cause actuation of said switch in opposite directions, a fixed support, a lever mounted on said support through a slip friction pivot for supporting said first arm and said switch, and means for rotating said lever about said pivot to cause motion of said projection lengthwise of said opening and thereby vary said differential.

3. In combination, a switch operable between open and closed positions, a first arm for operating said switch, a sensitive condition responsive element, a second arm connected to said element for rotation thereby upon variations in said condition, one of said arms having an opening of varying Width therein and the other of said arms carrying a projection entering said opening to form a lost motion connection, said element causing transverse motion of said projection in said opening to provide a differential between the values of said condition which cause actuation of said switch in opposite directions, a fixed support, mean mounted on said fixed support for bodily shifting said first arm and said switch to cause motion of said projection lengthwise of said opening and thereby vary said differential, means for yieldably restraining said shifting means, and a connection between said first arm and said shifting means for permitting free transverse movement of said projection in said opening, thereby preventing transmission of torque from said shifting means to said sensitive element.

4. In a device of the character described, a fixed support, a differential adjusting member pivotally mounted on said support, a mercury switch'carrier pivoted on said member, a mercury switch mounted on said carrier, an arm adapted to be rotated in response to the variations in the value of a variable condition, a lost motion connection between said arm and carrier comprising a tapered slot in said arm and a projection on said carrier extending within said slot, and means for rotating said member whereby the amount of lost motion and hence the differential of operation of said switch is varied.

5. In a device of the character described, a fixed support, a differential adjusting member pivotally mounted on said support, a mercury switch carrier pivoted on said member, a mercury switch mounted on said carrier, an arm adapted to be rotated in response to the variations in the value of a variable condition, a lost motion connection between said arm and carrier comprising a tapered slot in said arm and a proiection on said carrier extending within said slot, and means for rotating said member whereby the amount of lost motion and hence the differential of operation of said switch is varied, said tapered slot being so shaped that the adjustment of said member will not aifect the condition value at which said switch is actuated in one direction.

6. In a device of the character described, a fixed support, a differential adjusting member pivotally mounted on said support, a mercury switch carrier pivoted On said member, a mercury switch mounted on said carrier, an arm adapted to be rotated in response to the variations in the value of a variable condition, a lost motion connection between said arm and carrier comprising a tapered slot in said arm and a projection on said carrier extending within said slot, means for rotating said member whereby the amount of lost motion and hence the differential of operation of said switch is varied, stops on said fixed support to limit the amount of rotary movement of which said member is capable, and means for indicating the relative position of said member and hence the differential of operation of said switch.

STEPHEN CRUM. 

